1. Field of the Invention
The present invention relates to a manufacturing method of a liquid jet recording head for performing recording on a recording medium by discharging recording liquid from its minute discharge port as liquid droplets.
2. Related Background Art
A typical example of a liquid jet recording apparatus of a so-called non-impact recording type is comprised of a liquid jet recording head for executing recording on a recording medium, and a recording liquid supply system for supplying the recording liquid to the recording head. In the liquid jet recording head, an electrothermal converting element is used as an element for generating discharge energy, and droplets of the recording liquid are discharged from its minute discharge port by the discharge energy.
Further, as a liquid jet recording head using an electrothermal converting system, there have been proposed a system wherein droplets are discharged in a direction parallel to a board plane on which plural electrothermal converting elements are arranged, and a system wherein droplets are discharged in a direction perpendicular to a board plane on which plural electrothermal converting elements are arranged.
FIGS. 29A to 29C illustrate a board (also referred to as a recording element board) on which a plurality of general electrothermal converting elements are arranged, and which functions to discharge liquid droplets. FIGS. 29A, 29B and 29C are its plan view, its bottom view, and its side view, respectively. FIG. 30 is a view illustrating a state in which the recording element board of FIGS. 29A to 29C is connected to a wiring board.
As illustrated in FIGS. 29A to 29C, a recording element board 101 is equipped with a through hole (a recording liquid supply port) 103 for supplying recording liquid from its bottom side. A plurality of electrothermal converting elements (not shown) for imparting discharge energy to the recording liquid are arranged on both sides of the through holes 103 on the surface of a board 102, respectively. Further, a discharge plate 105 is placed on the board 102, and plural discharge ports 106 facing the respective electrothermal converting elements are formed in the discharge plate 105. Plural electrodes 107 are further provided on both end portions of the surface of the board 102, and the electrodes 107 are electrically connected to the electrothermal converting elements, respectively.
Further, as illustrated in FIG. 30, plural electrodes 107 formed on the recording element board 101 are electrically connected to plural respective leads 113 formed on a flexible film wiring board 111 by TAB techniques, for example. A recording element unit 120 is thus constructed. The entire electrical connecting portion is protectively covered with sealing resin 119 so as to be protected from corrosion by the recording liquid and wiring breakage by external force.
FIGS. 31A and 31B exemplify a conventional liquid jet recording head equipped with the recording element unit as illustrated in FIG. 30. FIG. 31A is its perspective view, and FIG. 31B is a cross-sectional enlarged view taken along the line A—A in FIG. 31A.
As illustrated in FIG. 31B, the recording element unit is bonded to the upper surface of a support member 108 with adhesive resin 121. Further, a support plate 109 is bonded to the upper surface of the support member 108 by adhesive resin 122, and the flexible film wiring board 111 is bonded to the upper surface of the support plate 109 by adhesive resin 123. Furthermore, fixed to the side surface of the support member 109 is a second wiring board 116 which is provided with external input pads 115 for supplying electrical signals, such as recording information, to the liquid jet recording head from the side of a body of the recording apparatus. The second wiring board 116 is electrically connected to each recording element unit through the flexible film wiring board 111a, 111b, 111c, or 111d. 
As illustrated in FIG. 31B, a recess portion 117 formed between the support plate 109 and the recording element board 101 is protectively covered with first sealing resin 118 so as to prevent corrosion by the recording liquid and short circuit through the recording liquid.
FIG. 32 is a cross-sectional view illustrating another conventional liquid jet recording head.
As illustrated FIG. 32, the through port (a recording liquid supply port) 103 is formed in the board 102 to supply the recording liquid from its bottom surface, plural discharge energy generating elements (for example, electrothermal converting elements) 104 for imparting discharge energy to the recording liquid are arranged on both sides of the through hole (the recording liquid supply port) 103 on the surface of the board 102, respectively. Further, a discharge port plate 105 is placed on the board 102, and plural discharge ports 106 facing the respective electrothermal converting elements are formed in the discharge port plate 105. Plural electrodes (not shown) are further provided on both end portions of the surface of the board 102, and the electrodes are electrically connected to the electrothermal converting elements, respectively.
Further, a support plate 109 is bonded to the upper surface of the support member 108, and a base film 124 comprising the flexible film wiring board 111 is bonded to the upper surface of the support plate 109 with resist 125. The flexible film wiring board 111 is electrically connected to the recording element board 101. A recess portion 117 formed between the support plate 109 and the recording element board 101 is protectively covered with first sealing resin 118 so as to prevent corrosion by the recording liquid and short circuit through the recording liquid. Furthermore, an electrical connecting portion between the electrode (not shown) on the recording element board 101 and an electrode lead (not shown) on the flexible film wiring board 111 is protectively covered with second sealing resin (not shown). Moreover, an outer periphery of the flexible film wiring board 111 bonded to the support plate 109 is protectively covered with third sealing resin 127 to prevent corrosion by the recording liquid.
Japanese Patent Application Laid-Open No. 2001-130001 discloses a conventional resin sealing method using the first sealing resin and the second sealing resin. In an ink jet recording head disclosed in this Japanese reference, after the first sealing resin is packed, the viscosity of the resin is lowered by raising its temperature up to temperatures a little above room temperature such that the resin can be liquidized and packed all over, and the resin is then thermally treated at curing temperature for a predetermined time. Alternatively, after the first sealing resin is liquidized and packed as described above, second sealing resin with higher viscosity and lower fluidity is laid on a predetermined place, and both the first and second resins are then thermally treated at curing temperature for a predetermined time.
In the thus-constructed conventional liquid jet recording head, the first heat treatment is for lowering the viscosity of the first sealing resin and fluidizing it, and the next heat treatment is for curing the overall sealing resins.
Further, Japanese Patent Application Laid-Open No. 2002-19120 discloses another conventional resin sealing method using the first sealing resin and the second sealing resin. In a liquid jet recording head disclosed in this Japanese reference, first resin having resiliency after cured or hardened is laid in recess portions formed between opening portions of the flexible film wiring board and the support plate, and the periphery of the recording element board, and second resin is then laid after the first resin is cured. The second resin is capable of strongly bonding and firmly covering the electrical connecting portion between the recording element board and the flexible film wiring board.
In the thus-constructed conventional liquid jet recording head (see FIGS. 19 and 20, for example), the first resin 18 packed in recess portions formed between opening portions of the flexible film wiring board and the support plate 9, and the periphery of the recording element board 1 has resiliency after cured, and accordingly even when the first resin is cured and contracted, there is no fear that cracks and the like occur in the recording element board 1. Further, since the electrical connecting portion between the recording element board 1 and the flexible film wiring board is sufficiently covered with the firm second resin 19, the electrical connecting portion is protected against external forces such as wiping force.
In other words, the first sealing resin 18 is required to have resiliency after cured and be capable of being packed even in a narrow space, and generally silicon-denatured epoxy resin can be optimally used as the first sealing resin. The second sealing resin 19 is required to effect protection from external forces such as wiping force, and cover an uneven electrical connecting portion under a smooth condition such that a wiper can be prevented from being damaged during the wiping operation, and therefore epoxy resin, especially dam agent (which is resin agent capable of being firm after cured and maintaining the shape subsequent to coating), is most suitable.
Further, in the construction of the head, when the first sealing resin 18 is laid in recess portions formed between opening portions of the flexible film wiring board and the support plate 9, and the periphery of the recording element board 1, the first sealing resin 18 is likely to go underneath the electrical connecting portion between the recording element board 1 and the flexible film wiring board, and the electrode lead 13 as well. Basically, this access is necessary access since portions underneath the electrical contact and the electrode lead 13 are planned to be sealed by such access. In order to gain access to a narrow space underneath the electrode lead 13, the access needs to be executed using the first sealing resin 18 having good fluidity. The second sealing resin 19 is the dam agent with poor fluidity, and therefore a narrow space, such as a space underneath the electrode lead 13, cannot be filled with the second sealing resin. Accordingly, two sealing resins have to be employed, and hence a boundary interface inevitably appears between the first sealing resin 18 and the second sealing resin 19 in the electrical connecting portion.
In the above-discussed structure, there exist the first sealing resin 18 and the second sealing resin 19, and the boundary interface between the first sealing resin 18 and the second sealing resin 19 in the electrical connecting portion, and therefore the electrical connecting portion needs to be completely sealed such that the interface can be protected against external attacks of ink and so forth.
Further, the above construction can be fabricated by a method in which after the recess portion is filled with the first resin 18, the electrical connecting portion is covered with the second resin 19, and the first resin 18 and the second resin 19 are then cured simultaneously. Thereby, its productivity efficiency can be improved as compared with the case where the first resin 18 and the second resin 19 are successively cured.
The first resin 18 can be thermosetting silicon-denatured epoxy resin, and the second resin 19 can be thermosetting epoxy resin.
The above-discussed conventional manufacturing methods of liquid jet recording heads, however, have the following disadvantages.
After the first sealing resin (thermosetting silicon-denatured epoxy resin) 18 is laid, the second sealing resin (thermosetting epoxy resin) 19 is superposed on the uncured first sealing resin 18. The two sealing resins are then cured simultaneously. For this reason, a compatible layer 29 is formed at a boundary portion between the first sealing resin 18 and the second sealing resin 19. Cases may occur where curing obstruction occurs and the compatible layer 29 cannot be cured enough to seal a necessary portion.
Further, the boundary layer (a bonded interface) between the first sealing resin 18 and the second sealing resin 19 is present in the electrical connecting portion in the above structure, and accordingly electrical connecting defects threaten to occur due to undesired access of ink and the like from the outside if the compatible layer 29 establishes communication between the outside and the electrode lead 13, or the electrical connecting portion (see FIG. 19).
In order to solve such disadvantages, it can be considered that the first sealing resin 18 is laid covering the electrical connecting portion and the electrode lead 13 such that the boundary layer between the first sealing resin 18 and the second sealing resin 19 cannot go over the electrical connecting portion.
However, if the second sealing resin 19 is laid after the first sealing resin is laid under its uncured condition, the second sealing resin 19 is liable to sink in the first sealing resin 18 and reach the electrode lead 13 and the electrical connecting portion. Resultantly, the boundary layer between the first sealing resin 18 and the second sealing resin 19 is still likely to appear in the electrical connecting portion. When the compatible layer 29 exists in such boundary layer, the electrical defect likewise occurs.
Furthermore, in order to solve the above disadvantages, it can be considered that the second sealing resin 19 is laid after the first sealing resin 18 is completely cured. However, if the first sealing resin 18 is completely cured, its retraction is likely to appear between leads and the like due to its curing contraction. The second sealing resin 19 having high viscosity serving as the dam agent cannot enter the retraction portion, and air voids are likely to appear in the electrode leads 13 and the electrical connecting portion to lower the sealing function. Further, the air void is likely to expand and rupture when the overall sealing resin is completely cured, and holes are likely to be created in the second sealing resin 19, thereby damaging the sealing function.
Additionally, in the method wherein the first sealing resin 18 is completely cured, two curing steps for complete curing are needed for the first sealing resin 18 and the second sealing resin 19, respectively. Accordingly, its productivity efficiency is remarkably lowered.
As described in the foregoing, the first sealing resin 18 and the second sealing resin 19 need to have different characteristics and functions in the light of the head structure. Therefore, similar problems are posed in connection with the bonding between different sealing resins, like the case where the above-discussed silicon-denatured epoxy rein and epoxy resin are used.